1. The Field of the Invention
The present invention relates to water evaporation systems, more particularly to pond-type water evaporation systems for large-scale evaporation of waste water from industrial sources.
2. The Relevant Technology
There are many industrial processes which produce large quantities of water that cannot be legally discharged into rivers, other bodies of water, or onto the ground but must be impounded in evaporation ponds. Examples include waste water produced during the drilling of oil and gas wells, as a byproduct of extracting oil and gas (e.g., natural subsurface water or injected water), farm runoff (e.g., crop irrigation runoff, such as in the Imperial Valley in California, hog farm runoff, cattle farm runoff, and winery waste water), mine tailings wash runoff, mine process waste water (e.g., from gold mining, which water includes cyanide salts and acids), food processing waste water, sewage water, mineral reclamation evaporation ponds (e.g., to recover potash, soda ash, gypsum, magnesium and salt), and waste water discharged from mineral reclamation (e.g., alkaline water in trona ponds resulting from mining soda ash).
Waste water is produced in large quantities during drilling and extraction of natural gas and petroleum. Water is often used during well drilling, which produces contaminated waste water that must be impounded. Petroleum and gas reservoirs often contain edge water, which is natural subterranean water located near the hydrocarbon being extracted. In addition, many producers inject water into the ground (e.g., as a peripheral water drive) in order to drive the oil or gas toward producing wells within the periphery of water injectors. The amount of water extracted as a byproduct of gas or oil production is a fraction of the water cut. The water cut produced from oil and gas wells is typically separated from the oil or gas near the well head and stored in a holding tank. Because the water contains contaminants, it is typically hauled to a licensed impoundment facility for disposal in a lined evaporation pond.
Because evaporation of pond water is generally passive, impoundment ponds are typically very large, sometimes covering up to 50 acres or more to increase the rate of evaporation. The waste water contained in such ponds is often toxic. For these and other reasons, waste water evaporation ponds must generally be placed at remote locations, away from cities, roads, parks and other places where people are likely to congregate. Moreover, industrial waste water impoundments can attract and kill migratory birds and other wildlife. As a result, many locales ban the construction of large water impoundment ponds for environmental and/or safety reasons. For example, water produced at oil and gas wells in Colorado is often shipped to other locations for disposal, such as Utah, at a cost of about $10 to $12 for each barrel of water. About 100,000 barrels of waste water are currently shipped daily from Colorado to Utah, at a total cost of $1,000,000 or more per day.